The present invention relates to a plating apparatus for plating a substrate such as a semiconductor wafer or the like, and particularly to a substrate plating apparatus for forming a wiring layer in a wiring portion comprising fine channels and/or fine holes formed in the surface of a substrate.
Aluminum wiring is well known for its common use as the wiring material for forming circuits in semiconductor devices. One of the most common methods for forming wiring patterns in a semiconductor device has been the etch-back method of an aluminum layer which is sputtered thereon. However, this method can be very difficult when forming wiring patterns using other metal materials, such as copper or the like. In this case, the common method is to form channels and holes for wiring in the substrate, implant metal material in the channels and holes, and subsequently perform chemical mechanical polishing (CMP) on the surface of the substrate.
However, as the level of integration in semiconductor devices increases, forcing a finer pattern in wiring scale as well as in the width of the wires, the step coverage increases and conventional methods of sputtering are limited in their ability to implant metal into a wiring area composed of fine channels and holes (fine contact holes). There is a tendency for voids to be formed in the wiring area.
Due to the increased functionality of semiconductor devices, it is necessary to form wiring channels and wiring holes having widths of 0.18 xcexcm or 0.13 xcexcm. However, it is difficult to implant metal materials in such miniaturized channels and holes using the sputtering method. Therefore, it is required to develop a new technique to use in place of sputtering. This technique will use one apparatus to perform either electrolytic plating or electroless plating to form a copper (Cu) plated layer on the surface of a semiconductor wafer including a wiring area having these type of fine channels and holes. The technique will include a process for removing the Cu plated layer from the surface of the semiconductor wafer while leaving a Cu plated layer in the wiring area.
Further, if the Cu plating apparatus and the CMP apparatus are provided separately, the surface of the Cu plating film may oxidize or particles may be attached on the surface when the device is exposed to the air after the plating and cleaning processes.
Further, when the Cu plating apparatus and the CMP apparatus are separated, an extra drying process is needed. That is, after the semiconductor wafer has been plated in the Cu plating apparatus, the wafer is dried and transported out of the apparatus. The wafer is then conveyed into the CMP apparatus in its dried state. If an additional cover plating apparatus is required separately to form a cover plating over the top of the wire plated layer, the wafer must again be dried before being conveyed to the cover plating apparatus. In addition, oxidation on the surface of the wire plated layer progresses more with the passage of time.
Further, when forming a seed layer as a preprocess to the plating process using electroless Cu plating or electrolytic Cu plating having different liquid components, the semiconductor wafer is dried after completing these plating processes and inserted into a wafer cassette to be moved between apparatuses. However, it is possible to eliminate the drying process and the like by introducing the semiconductor wafer into the Cu plating apparatus while still coated with cleaning solution, that is, while the wafer is still wet. Feeding the semiconductor wafers continuously one by one into the Cu plating apparatus without drying and inserting the wafers into cassettes will reduce the amount of wafer contamination.
After the semiconductor wafers are introduced one at a time into the Cu plating apparatus, there is a waiting period before the wafers are plated. During this time the wafers can become contaminated with particles and an oxidation film may form on the surface. To prevent this from occurring, the wafers can be temporarily stored in pure water or dilute sulfuric acid, thereby eliminating the need to set a non-conducting time for removing the oxidized film from the surface of the wafer after immersing the wafer in plating solution.
Further, as the thickness of the seed layer in the holes becomes thinner due to the finer patterns of semiconductor devices, it is essential that etching processes for removing oxidized layers are reduced as much as possible. That is, it is important to minimize the formation of oxidized film before the plating process is conducted.
After the plating process is completed, the semiconductor wafers are continuously discharged one by one from the Cu plating apparatus and loaded into the CMP apparatus for the next process. Even though the Cu plating apparatus is separate from the CMP apparatus, by installing the CMP apparatus close to the Cu plating apparatus, it is possible to eliminate the unloading stage and, in some cases, the drying process, thereby reducing the amount of installation area required for the equipment.
In view of the foregoing, it is an object of the present invention to provide a substrate plating apparatus capable of forming a plating layer on the surface of a substrate and storing the substrate until the next process in a way that the substrate is not exposed to the atmosphere.
It is another object of the present invention to provide a substrate plating apparatus that can be easily configured to execute all steps continuously, including a process of forming a plating layer on the surface of a substrate and a CMP process which includes a wet process in which the plated layer is removed from the surface of the substrate without removing the plated layer from the wiring area.
It is another object of the present invention to provide a substrate plating apparatus not only capable of performing a process of introducing semiconductor wafers continuously one by one into the plating apparatus without loading the wafers into cassettes, but also capable of preventing particle contamination and the formation of oxidized film on the surface of the wafers, reducing the number of processes and reducing the installation area required for the apparatus.
These and other objects will be attained by a substrate plating apparatus having a plating process section for plating a surface of a substrate and a washing process section for washing the substrate after the substrate has been plated in the plating process section. The substrate plating apparatus comprises a substrate storage vessel containing a storing solution for storing the substrate in an immersed state after the substrate has been washed in the washing process section.
With this construction, the substrate storage vessel provided for immersing the substrate after the plating and washing processes prevents the substrate from being exposed to the air after being plated and before undergoing the next processing step. Accordingly, the present invention can prevent particle contamination and the formation of an oxidized film on the surface of the substrate.
According to another aspect of the present invention, there is provided a substrate plating apparatus having a plating process section for plating a substrate comprising an underwater substrate conveyor for conveying the substrate through a water channel containing flowing pure water after the substrate has been plated in the plating process section.
With this construction, the present invention enables transport of the substrate to the location of the next process without exposing the substrate to the air. Further, such wet and dry processes as CMP or washing processes can be provided at the downstream end of the substrate conveyor. Accordingly, it enables easy configuration of equipment capable of continuously conducting all processes, including wet processes, such as a plating process for forming a plating layer on the surface of the substrate, a CMP process for removing the plated layer from the surface of the substrate, leaving only the plating in the wiring section, and the like.
According to another aspect of the present invention, there is provided a substrate plating apparatus having a plating process section for plating a substrate and a washing process section for washing the substrate with a washing solution after the substrate has been plated in the plating process section. The apparatus comprises a substrate conveyor disposed in the substrate plating apparatus for loading substrates into the substrate plating apparatus and discharging substrates out of the substrate plating apparatus, or for performing at least one of the operations of loading or discharging the substrates. A plurality of the substrates to be plated in the plating process section are loaded into the substrate plating apparatus one at a time, plated in the plating process section, washed in the washing process section, and subsequently discharged one at a time from the substrate plating apparatus.
With this construction, when conducting a preprocess before the plating process, such as forming a seed layer using Cu electroless plating or electrolytic plating with differing liquid components, it is not necessary to dry the wafer, insert wafers into wafer cassettes, or transfer wafer cassettes between apparatuses after the wafers have been plated and washed. Instead, the wafers can be handled while still coated with cleaning solution, thereby eliminating the drying process. As a result, it is possible to reduce the overall equipment scale required to perform the processing.